We are redoing our bathroom and have just finished installing the Hardibacker board and are just about to start mortaring the joints. However, I have an awful feeling that we are about to make a huge mistake (or several):

2. I'm figuring out the thickness of the finish wall for the shower fixture installation. The tiles are 3/8" thick. Together with the thickness of the mortar, what will be the total thickness of my finished wall? I'm guessing the mortar doesn't really end up being 1/2" right?

3. Is there any problem with 1/8" grout lines with tile this large?

4. Anything else I am overlooking? Yes, I'm a first-timer and yes, I know we picked very difficult tile size to work with.

3. That depends on how consistent the tiles are. You might be better to go with 3/16" to allow for minor differences in the size of the tile. Also, if you're planning to install in some type of pattern, keep in mind that sometimes those tile have a bit more crowning than normal. Two things you have to deal with in this case: Coverage, because the center of the tile is a little higher than the edges, and keeping the tiles level with each other. The 1/2' trowel will help with these issues.

4. I would probably tape and mud the joints as the tile are installed. This might keep you from having a slight hump where the joints are, further causing you problems in leveling.

Hello, we are planning to tile with large (12 x 24) porcelain tile and I've asked a couple of questions here before.

Here's a new issue: We bought prefabbed nitcho shelves for the bathtub surround. They are nice and level and installed to the studs. We installed the Hardibacker board around them, but in one section, the joint is really not flush/straight.

I do not understand why, since the meeting joint is obviously screwed into the same stud. But sure enough, the piece on the left is about 1/8" proud of the piece on the right (please see picture, if it worked, having upload issues).

We are just about to start mortaring our joints, but I've seen enough advice on this forum that says make sure your subsurface is STRAIGHT! Especially with larger, unforgiving tile (and we're planning on small 1/8" grout lines).

Is there something I need to do to straighten this joint, or will the mortar be forgiving if I slather it thicker in that section?

Hello Eric,
I wouldn't use thicker mortar to tape your joints, it will just cause more problems.

It's hard to tell what's going on from your pics. Is that two pieces of 1/2" Hardi side by side?

If it were me, I would just use a larger notch trowel to set the tile, it will help you get up and over any imperfections in the substrate. If you're worried about mortar squishing up through the joints, just flat trowel the cement board, and notch trowel the backs of the tile.

Thank you for your help. Yes, those are Hardibacker 500 (1/2") side-by-side.

So flat troweling it after the joints are mortared and dried won't give me too much mortar under the tile?

Thanks again!

You're welcome, that's what we're here for.

When I say "flat trowel", I mean apply mortar with the flat side of the trowel, and then basically "scrape" the flat side of the trowel over the area again with the trowel held at an approximately 45 degree angle, to force mortar into the substrate and remove any excess. So to answer your question, no, it won't give you too much mortar under the tile. Most pros refer to this step as "burning in", and most do it even if you're going to notch trowel the substrate. It helps to force mortar into the pores of the substrate, giving you a good mechanical bond.

Forgive me, I know this question is basic, but I know it will help others who are just starting just by the basic title of this post.

I've been told and have read about "back buttering" tiles if working with a bigger trowel and/or bigger tile size. Here are my basic questions:

1. What is the advantage of back buttering versus troweling the backer board instead? Or does back buttering mean that I apply mortar to both surfaces like a good PB&J sandwich? (yeah, it's almost lunch time!)

2. Do I back butter with the lines going horizontal or vertical?

Thank you again for all this advice. Reading this forum is better than any book I found in the big box stores.

1. What is the advantage of back buttering versus troweling the backer board instead? Or does back buttering mean that I apply mortar to both surfaces like a good PB&J sandwich? (yeah, it's almost lunch time!)

gives you better coverage and a thicker bed to set the lager tile flat.

Quote:

2. Do I back butter with the lines going horizontal or vertical?

you can flat trowel on a thin layer of thinset or use the notches. doesnt matter as long as you have coverage.

Before you set that first tile, grab a 4 foot level (6 foot would be better) and start checking the walls for plumb. I am guessing you will find the walls tilt in, out top to bottom, bow or cup in the center. Find the part of each wall that sticks out the furthest. Mark that spot. Compare how far out that spot is to the rest of the wall. Before I get too far off course with advice, give us some pics and feedback on how out of plumb the walls are.

Remember; where you place your first tile determines where your last tile goes.

I've combined your threads here so folks can see what you're working on and what's been previously asked and answered. We can change the title to something more generic for your project any time you'd like.

It's been said before but I'll say it again...please don't start new threads for every question you have. We have a "one project, one thread" policy here on the JB Forums and we'd like you to adhere to that policy. Ask ALL questions regarding your project and anything you encounter while working on that project on this thread.

Now for the thinset. I would start over. I know isn't good to add water after the initial slake and I can't imagine adding more thinset would be good either now that the hydration and chemical process has started.